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fully integrated signal processor optimized for car radio applica- tions fully programmable by i 2 c bus includes audioprocessor, stereo - decoder with noise blanker and multipath detector programmable roll-off compensa- tion no external components description the TDA7400d is the newcomer of the csp fam- ily introduced by tda7460/61. it uses the same innovative concepts and design technologies al- lowing fully software programmability through i 2 c bus and overall cost optimisation for the system designer. the device includes an audioprocessor with con- figurable inputs and absence of external compo- nents for filter settings, a last generation stereodecoder with multipath detector and a so- phisticated stereoblend and noise cancellation circuitry. strength points of the csp approach are flexibility and overall cost/room saving in the application, combined with high performances. audio processor part july 1999 ? supply demodulator + stereo adjust + stereo blend cref mpin out lr d98au852b digital control pilot cancellation v s tape l input multiplexer + auto zero ph- mpx volume bass treble out lr out lf out rr out rf out lf out rr out rf scl sda 80khz lp pll 25khz lp s&h high cut control multipath- detector pulse former d mpout level cdl cdgnd cdr am tape r ph+ gnd smute soft mute pil det i 2 c bus noise blanker a mux r mux l acoutl acoutr acinrf acinrr 531 10 44 43 8 7 12 27 26 42 15 16 14 30 32 29 31 23 24 19 18 38 39 35 34 22 v ref 41 muxr muxl fm_r fm_l cdlout 4 cdrout 2 qual. acinlf acinlr 37 40 qual 21 block diagram tqfp44 ordering number: TDA7400 TDA7400 advanced car signal processor 1/28
absolute maximum ratings symbol parameter value unit v s operating supply voltage 10.5 v t amb operating ambient temperature range -40 to 85 c t stg operating storage temperature range -55 to 150 c supply symbol parameter test condition min. typ. max. unit v s supply voltage 7.5 9 10 v i s supply current v s =9v 253035ma svrr ripple rejection @ 1khz audioprocessor (all filters flat) 50 60 db stereodecoder + audioprocessor 45 55 db esd all pins are protected against esd according to the mil883 standard. thermal data symbol parameter value unit r th-j pins thermal resistance junction-pins max 65 c/w 1 2 3 5 6 4 7 8 9 10 17 11 18 19 20 21 22 44 43 42 41 39 40 38 37 36 35 34 28 27 26 24 23 25 33 32 31 29 30 n.c. cdl cdlout cdrout cdr cdg n.c. am n.c. phone- phone+ mpx n.c. level mpin n.c. mpout muxl muxr n.c. qual smute tape r tape l cref v ref acinrf acinlf acinrr acinlr n.c. acoutl acoutr n.c. v s gnd sda scl n.c. n.c. out lf out rf out rr out lr d98au853 12 13 14 15 16 pin connection TDA7400 2/28
pin description n. name function type 1 vref reference voltage output i 2 cref reference capacitor pin s 3 tapel tape input left i 4 taper tape input right i 5 cdr cd right channel input i 6 cdgnd cd input common ground i 7 cdl cd input left channel i 8 ph - differential phone input - i 9 ph + differential phone input + i 10 am am input i 11 mpx fm stereodecoder input i 12 level level input stereodecoder i 13 mpin multipath input i 14 mpout multipath output o 15 muxl multiplexer output left channel o 16 muxr multiplexer output right channel o 17 qual stereodecoder quality output o 18 smute soft mute drive i 19 scl i 2 c clock line i 20 sda i 2 c data line i/o 21 gnd supply ground s 22 vs supply voltage s 23 outrr right rear speaker output o 24 outlr left rear speaker output o 25 outrf right front spaeaker output o 26 outlf left front speaker output o 27 acoutr pre-speaker ac output right channel o 28 acoutl pre-speaker ac output left channel o pin type legenda: i = input o = output i/o = input/output s = supply nc = not connected TDA7400 3/28
input multiplexer quasi-differential cd and cassette stereo input am mono input phone differential input multiplexer signal after in-gain available at separate pins volume control 1db attenuator max. gain 15db max. attenuation 79db bass control 2nd order frequency response center frequency programmable in 4(5) steps dc gain programmable 15 x 1db steps treble control 2nd order frequency response center frequency programmable in 4 steps 15 x 1db steps speaker control 4 independentspeaker controls in 1db steps max gain 15db max. attenuation 79db mute functions direct mute digitally controlled softmute with 4 programmable mute time description of the audioprocessor part electrical characteristics (v s = 9v; t amb =25 c; r l = 10k w ; all gains = 0db; f = 1khz; unless otherwise specified). symbol parameter test condition min. typ. max. unit input selector r in input resistance all inputs except phone 70 100 130 k w v cl clipping level 2.2 2.6 v rms s in input separation 80 100 db g in min min. input gain -1 0 1 db g in max max. input gain 13 15 17 db g step step resolution 0.5 1 1.5 db v dc dc steps adjacent gain step -5 0.5 5 mv g min to g max -10 5 10 mv differential cd stereo input r in input resistance differential 70 100 130 k w common mode 70 100 130 k w cmrr common mode rejection ratio v cm =1 vrms @ 1khz 45 70 db v cm =1 vrms @ 10khz 45 60 db e n output noise @ speaker outputs 20hz to 20khz flat; all stages 0db 615 m v differential phone input r in input resistance differential 40 56 k w cmrr common mode rejection ratio v cm =1 vrms @ 1khz 40 70 db v cm =1 vrms @ 10khz 40 60 db TDA7400 4/28
electrical characteristics (continued) symbol parameter test condition min. typ. max. unit volume control g max max gain 13 15 17 db a max max attenuation 70 79 db a step step resolution 0.5 1 1.5 db e a attenuation set error g = -20 to 20db -1.25 0 1.25 db g = -60 to 20db -4 0 3 db e t tracking error 2db v dc dc steps adjacent attenuation steps 0.1 3 mv from 0db to g min 0.5 5 mv soft mute a mute mute attenuation 80 100 db t d delay time t1 0.48 1 ms t2 0.96 2 ms t3 20 40.4 60 ms t4 200 324 600 ms v thlow low threshold for sm pin 1 1v v thhigh high threshold for sm pin 2.5 v r pd internal pull-up resistor 70 100 130 k w bass control c range control range 13 15 17 db a step step resolution 0.5 1 1.5 db f c center frequency f c1 54 60 66 hz f c2 63 70 77 hz f c3 72 80 88 hz f c4 90 100 (150) (2) 110 hz q bass quality factor q 1 0.9 1 1.1 q 2 1.1 1.25 1.4 q 3 1.3 1.5 1.7 q 4 1.8 2 2.2 dc gain bass-dc-gain dc = off -1 0 1 db dc = on 3.5 4.4 5.5 db treble control c range control range 13 15 17 db a step step resolution 0.5 1 1.5 db f c center frequency f c1 8 10 12 khz f c2 10 12.5 15 khz f c3 12 15 18 khz f c4 14 17.5 21 khz 1) the sm pin is active low (mute = 0) 2) see note in programming part TDA7400 5/28
electrical characteristics (continued) symbol parameter test condition min. typ. max. unit speaker attenuators r in input impedance 35 50 65 k w g max max gain 13 15 17 db a max max attenuation -70 -79 db a step step resolution 0.5 1 1.5 db a mute output mute attenuation 80 90 db e e attenuation set error 2db v dc dc steps adjacent attenuation steps 0.1 5 mv audio outputs v clip clipping level d = 0.3% 2.2 2.6 v rms r l output load resistance 2 k w c l output load capacitance 10 nf r out output impedance 30 120 w v dc dc voltage level 4.3 4.5 4.7 v general e no output noise bw = 20 hz to 20 khz output muted 315 m v bw = 20 hz to 20 khz all gain = 0db 6.5 15 m v s/n signal to noise ratio all gain = 0db flat; v o =2v rms 102 110 db bass treble at 12db; a-weighted; v o = 2.6v rms 96 100 db d distortion v in =1v rms ; all stages 0db 0.002 0.1 % v in =1v rms ; bass & treble = 12db 0.05 0.1 % s c channel separation left/right 80 100 db e t total tracking error a v = 0 to -20db -1 0 1 db a v = -20 to -60db -2 0 2 db bus inputs v il input low voltage d = 0.3% 0.8 v v ih input high voltage 2.5 v i in input current v in = 0.4v -5 5 m a v o output voltage sda acknowledge i o = 1.6ma 0.4 v TDA7400 6/28
electrical characteristics (v s = 9v; deemphasis time constant = 50 m s, v mpx = 500mv(75khz deviation), fm= 1khz, gv = 6db, t amb =27 c; unless otherwise specified). symbol parameter test condition min. typ. max. unit v in mpx input level gv = 3.5db 0.5 1.25 v rms r in input resistance 70 100 130 k w g min min. input gain 1.5 3.5 4.5 db g max max. input gain 8.5 11 12.5 db g step step resolution 1.75 2.5 3.25 db svrr supply voltage ripple rejection v ripple = 100mv; f = 1khz 35 60 db a max. channel separation 30 50 db thd total harmonic distortion 0.02 0.3 % s + n n signal plus noise to noise ratio a-weighted, s = 2v rms 80 91 db mono/stereo-switch v pthst1 pilot threshold voltage for stereo, pth = 1 10 15 25 mv v pthst0 pilot threshold voltage for stereo, pth = 0 15 25 35 mv v pthmo1 pilot threshold voltage for mono, pth = 1 7 12 17 mv v pthmo0 pilot threshold voltage for mono, pth = 1 10 19 25 mv pll d f/f capture range 0.5 % deemphasis and highcut t hc50 deemphasis time constant bit 7, subadr, 10 = 0, v level >> v hch 25 50 75 m s t hc75 deemphasis time constant bit 7, subadr, 10 = 1, v level >> v hch 50 75 100 m s t hc50 highcut time constant bit 7, subadr, 10 = 0, v level >> v hcl 100 150 200 m s t hc75 highcut time constant bit 7, subadr, 10 = 1, v level >> v hcl 150 225 300 m s stereoblend-and highcut-control ref5v internal reference voltage 4.7 5 5.3 v tc ref5v temperature coefficient 3300 ppm l gmin min. level gain -1 0 1 db l gmax max. level gain 8 10 12 db l gstep level gain step resolution 0.3 0.67 1 db vsbl min min. voltage for mono 25 29 33 %ref5v vsbl max min. voltage for mono 54 58 62 %ref5v vsbl step step resolution 2.2 4.2 6.2 %ref5v vhch min min. voltage for no highcut 38 42 46 %ref5v vhch max min. voltage for no highcut 62 66 70 %ref5v vhch step step resolution 5 8.4 12 %ref5v vhcl min min. voltage for full highcut 12 17 22 %vhch vhcl max max. voltage for full highcut 28 33 38 %vhch vhcl step step resolution 2.2 4.2 6.2 %vhch stereodecoder part TDA7400 7/28
electrical characteristics (continued) symbol parameter test condition min. typ. max. unit carrier and harmonic suppression at the output a 19 pilot signal f = 19khz 40 50 db a 38 subcarrier f = 38khz 75 db a 57 subcarrier f = 57khz 62 db a76 subcarrier f = 76khz 90 db intermodulation (note 1) a 2f mod = 10khz, f spur = 1khz 65 db a 3f mod = 13khz, f spur = 1khz 75 db traffic ratio (note 2) a 57 signal f = 57khz 70 db sca - subsidiary communications authoorization (note 3) a 67 signal f = 67khz 75 db aci - adjacent channel interference (note 4) a 114 signal f = 114khz 95 db a 190 signal f = 190khz 84 db notes to the characteristics: 1. intermodulation suppression: a 2 = v o ( signal )( at1khz ) v o ( spurious )( at 1khz ) ;f s =( 2 x 10khz )- 19khz a 3 = v o ( signal )( at1khz ) v o ( spurious )( at 1khz ) ;f s =( 3 x 13khz )- 38khz measured with: 91% pilot signal; fm = 10khz or 13khz. 2. traffic radio (v.f.) suppression: measured with: 91% stereo signal; 9% pilot signal; fm=1khz; 5% subcarrier (f = 57khz, fm = 23hz am, m = 60%) a 57 ( v.w > f. )= v o ( signal )( at1khz ) v o ( spurious )( at 1khz + M - 23khz ) 3. sca ( subsidiary communications authorization ) measured with: 81% mono signal; 9% pilot signal; fm = 1khz; 10%sca - subcarrier ( fs = 67khz, unmodulated ). a 67 = v o ( signal )( at1khz ) v o ( spurious )( at 9khz ) ; f s =( 2 x 38khz )- 67khz 4. aci ( adjacent channel interference ): a 114 = v o ( signal )( at1khz ) v o ( spurious )( at 4khz ) ;f s = 110khz - ( 3 x 38khz ) a 190 = v o ( signal )( at1khz ) v o ( spurious )( at 4khz ) ;f s = 186khz - ( 5 x 38khz ) measured with: 90% mono signal; 9% pilot signal; fm =1khz; 1% spurious signal ( fs = 110khz or 186khz, unmodulated). TDA7400 8/28
electrical characteristics (continued) symbol parameter test condition min. typ. max. unit v tr trigger threshold 0) 1) meas. with v peak = 0.9v nbt = 111 (c) 30 (c) mv op nbt = 110 (c) 35 (c) mv op nbt = 101 (c) 40 (c) mv op nbt = 100 (c) 45 (c) mv op nbt = 011 (c) 50 (c) mv op nbt = 010 (c) 55 (c) mv op nbt = 001 (c) 60 (c) mv op nbt = 000 (c) 65 (c) mv op v trnoise noise controlled trigger threshold 2) meas. with v peak = 1.5v nct = 00 (c) 260 (c) mv op nct = 01 (c) 220 (c) mv op nct = 10 (c) 180 (c) mv op nct = 11 (c) 140 (c) mv op v rect rectifier voltage v mpx = 0mv nrd 6) = 00 0.5 0.9 1.3 v v mpx = 50mv; f = 150khz 1.5 1.7 2.1 v v mpx = 200mv; f = 150khz 2.2 2.5 2.9 v v rect dev deviation dependent rectifier voltage 3) means. with v mpx = 800mv (75khz dev.) ovd = 11 0.5 0.9(off) 1.3 v op ovd = 10 0.9 1.2 1.5 v op ovd = 01 1.7 2.0 2.3 v op ovd = 00 2.5 2.8 3.1 v op v rect fs fieldstrength controlled rectifier voltage 4) means. with v mpx = 0mv v level << v sbl (fully mono) fsc = 11 0.5 0.9(off) 1.3 v fsc = 10 0.9 1.4 1.5 v fsc = 01 1.7 1.9 2.3 v fsc = 00 2.1 2.4 3.1 v t s suppression pulse duration 5) signal holdn in testmode blt = 00 tbd 38 tbd m s blt = 10 tbd 32 tbd m s blt = 01 tbd 25.5 tbd m s blt = 00 tbd 22 tbd m s v rectadj noise rectifier discharge adjustment 6) signal peak in testmode nrd = 00 6) (c) 0.3 (c) v/ms nrd = 01 6) (c) 0.8 (c) v/ms nrd = 10 6) (c) 1.3 (c) v/ms nrd = 11 6) (c) 2.0 (c) v/ms sr peak noise rectifier charge signal peak in testmode pch = 0 7) (c) 10 (c) mv/ m s pch = 1 7) (c) 20 (c) mv/ m s (c) = by design/characterization functionally guaranteed through dedicated test mode structure noise blanker part internal 2nd order 140khz high pass filter programmable trigger threshold trigger threshold dependent on high frequency noise with programmable gain additional circuits for deviation and field- strength dependent trigger adjustment very low offset current during hold time due to opamps wmos inputs four selectable pulse suppression times programmable noise rectifier charge/discharge current TDA7400 9/28
electrical characteristics (continued) symbol parameter test condition min. typ. max. unit v adjmp noise rectifier adjustment through multipath 8) signal peak in testmode mpnb = 00 8) (c) 0.3 (c) v/ms mpnb = 01 8) (c) 0.5 (c) v/ms mpnb = 10 8) (c) 0.7 (c) v/ms mpnb = 11 8) (c) 0.9 (c) v/ms 0) all thresholds are measured using a pulse with t r =2 m s, t high =2 m s and t f =10 m s. the repetition rate must not increase the peak voltage. 1) nbt represents the noiseblanker byte bits d 2 ,d 0 for the noise blanker trigger threshold 2) nat represents the noiseblanker byte bit pair d 4 ,d 3 for the noise controlled triggeradjustment 3) ovd represents the noiseblanker byte bit pair d 7 ,d 6 for the over deviation detector 4) fsc represents the fieldstrength byte bit pair d 1 ,d 0 for the fieldstrength control 5) blt represents the speaker rr byte bit pair d 7 ,d 6 for the blanktime adjustment 6) nrd represents the configuration-byte bit pair d 1 ,d 0 for the noise rectifier discharge-adjustment 7) pch represents the stereodecoder-byte bit d 5 for the noise rectifier charge-current adjustment 8) mpnb represents the highcut-byte bit d 7 and the fieldstrength-byte d 7 for the noise rectifier multipath adjustment 65mv 30mv 8 steps noise controlled trig. threshold min. trig. threshold 260mv(00) 220mv(01) 180mv(10) 140mv(11) 0.9v vth 1.5v v peak(v) d97au648 figure 1. trigger threshold vs.v peak v peak (v op ) d97au649 20 deviation(khz) 0.9 1.2 2.0 2.8 detector off (11) 32.5 45 75 10 01 00 figure 2. deviation controlled trigger adjust- ment v op v in dc t r t high t f time d97au636 TDA7400 10/28
2.4v(00) 0.9v v peak e' d97au650 1.9v(01) 1.4v(10) mono stereo noisy signal good signal atc_sb off (11) noise ?3v figure 3. fieldstrength controlled trigger adjustment multipath detector internal 19khz band pass filter programmable band pass and rectifier gain two pin solution fully independent usable for external programming selectable internal influence on stereoblend electrical characteristics (continued) symbol parameter test condition min. typ. max. unit f cmp center frequency of multipath- bandpass stereodecoder locked on pilottono 19 khz g bpmp bandpass gain bits d 2 ,d 1 configuration byte = 00 6 db bits d 2 ,d 1 configuration byte = 10 12 db bits d 2 ,d 1 configuration byte = 01 16 db bits d 2 ,d 1 configuration byte = 11 18 db g rectmp rectifier gain bits d 7 ,d 6 configuration byte = 00 7.6 db bits d 7 ,d 6 configuration byte = 01 4.6 db bits d 7 ,d 6 configuration byte = 10 0 db bits d 7 ,d 6 configuration byte = 11 off db i chmp rectifier charge current bit d 5 configuration byte = 0 0.5 m a bit d 5 configuration byte = 1 1.0 m a i dismp rectifier discharge current 0.5 1 1.5 ma quality detector symbol parameter test condition min. typ. max. unit a multipath influence factor bit d 7 high-cut byte + bit d 7 fieldstrength byte + 00 01 10 11 0.7 0.85 1.00 1.15 TDA7400 11/28
input multiplexer cd quasi differential cassette stereo phone differential am mono stereodecoder input. input stages most of the input stages have remained the same as in preceeding st audioprocessors with excep- tion of the cd inputs (see figure 4). in the meantime there are some cd players in the market having a significant high source im- pedance which affects strongly the common- mode rejection of the normal differential input stage. the additional buffer of the cd input avoids this drawback and offers the full common- mode rejection even with those cd players. the output of the cd stage is permanently avail- able of the cd out-pins autozero in order to reduce the number of pins there is no ac coupling between the in-gain and the follow- ing stage, so that any offset generated by or be- fore the in-gain stage would be transferred or even amplified to the output. to avoid that effect a special offset cancellation stage called autozero is implemented. this stage is located before the volume-block to eliminate all offsets generated by the stereode- coder, the input stage and the in-gain (please notice that externally generated offsets, e.g. gen- erated through the leakage current of the cou- pling capacitors, are not cancelled). the auto-zeroing is started every time the data- byte 0 is selected and takes a time of max. 0.3ms. to avoid audible clicks the audioproces- sor is muted before the volume stage during this time. autozero remain in some cases, for example if the m p is executing a refresh cycle of the i 2 c bus programming, it is not useful to start a new autozero action because no new source is selected and an undesired mute would appear at the outputs. for such applica- tions the TDA7400d could be switched in the oauto zero remain modeo (bit 6 of the subad- dress byte). if this bit is set to high, the dat- abyte 0 could be loaded without invoking the autozero and the old adjustment value remains. multiplexer output the output signal of the input multiplexer is avail- able at separate pins (please see the blockdia- gram). this signal represents the input signal am- plifier by the in gain stage and is also going into the mixer stage. softmute the digitally controlled softmute stage allows muting/demuting the signal with a i 2 c bus pro- grammable slope. the mute process can either be activated by the softmute pin or by the i 2 c bus. the slope is realized in a special s shaped curve to mute slow in the critical regions (see fig- ure 5). for timing purposes the bit 3 of the i 2 c bus out- put register is set to 1 from the start of muting un- 15k 15k 100k cd+ cd- 15k 15k + - 15k 15k phone+ phone- 15k 15k + - d98au854a 100k 100k 100k stereodecoder in gain cassette am mpx 1 1 100k cd out figure 4. input stages TDA7400 12/28
til the end of demuting. bass there are four parameters programmable in the bass stage: (see figs 6, 7, 8, 9): attenuation figure 6 shows the attenuation as a function of frequency at a center frequency at a center fre- quency of 80hz. central frequency figure 7 shows the four possible center frequen- cies 60,70,80 and 100hz. quality factors figure 8 shows the four possible quality factors 1, 1.25, 1.5 and 2. dc mode in this mode the dc gain is increased by 5.1db. in addition the programmed center frequency and quality factor is decreased by 25% which can be used to reach alternative center frequencies or quality factors. treble there are two parameters programmable in the treble stage (see figs 10, 11): attenuation figure 10 shows the attenuation as a function of frequency at a center frequency of 17.5khz. center frequency figure 11 shows the four possible center fre- quency (10, 12.5, 15 and 17.5khz). speaker attenuator the speaker attenuators have exactely the same structure and range like the volume stage. functional description of stereode- coder the stereodecoder part of the TDA7400d (see fig. 12) contains all functions necessary to de- modulate the mpx signal like pilot tone depend- ent mono/stereo switching as well as ostereoblendo and ohighcuto functions. 1 ext. mute +signal ref -signal 1 i 2 c bus out time d97au634 figure 5. softmute timing 0.0 2.5 5.0 7.5 10.0 12.5 15.0 10.0 100.0 1.0k 10.0k figure 7. bass center @ gain = 14db, q = 1 -15.0 -10.0 -5.0 0.0 5.0 10.0 15.0 10.0 100. 0 1.0k 10.0k figure 6. bass control @ fc = 80hz, q = 1 note: please notice that a started mute action is always terminated and could not be interrupted by a change of the mute signal. TDA7400 13/28
stereodecoder mute the TDA7400d has a fast and easy to control rds mute function which is a combination of the audioprocessor's softmute and the high-ohmic mute of the stereodecoder. if the stereodecoder is selected and a softmute command is sent (or activated through the sm pin) the stereodecoder 0.0 2.5 5.0 7.5 10.0 12.5 15.0 10.0 100.0 1.0k 10.0k figure 9. bass normal and dc mode @ gain = 14db, fc = 80hz note: in general the center frequency, q and dc-mode can be set independently. the exception from this rule is the mode (5/xx1111xx) where the center frequency is set to 150hz instead of 100hz. 0.0 2.5 5.0 7.5 10.0 12.5 15.0 10.0 100.0 1.0k 10.0k figure 8. bass quality factors @ gain = 14db, fc = 80hz 0.0 2.5 5.0 7.5 10.0 12.5 15.0 10.0 100.0 1.0k 10.0k figure 11. treble center frequencies @ gain = 14db - 15.0 - 10.0 -5.0 0.0 5.0 10.0 15.0 10.0 100.0 1.0k 10. 0k figure 10. treble control @ fc = 17.5khz TDA7400 14/28
will be set automatically to the high-ohmic mute condition after the audio signal has been soft- muted. hence a checking of alternate frequencies could be performed. to release the system from the mute condition simply the unmute command must be sent: the stereodecoder is unmuted immedi- ately and the audioprocessor is softly unmuted. fig. 13 shows the output signal v o as well as the internal stereodecoder mute signal. this influ- ence of softmute on the stereodecoder mute can be switched off by setting bit 3 of the softmute byte to o0o. a stereodecoder mute command (bit 0, stereodecoder byte set to o1o) will set the stereodecoder in any case independently to the high-ohmic mute state. if any other source than the stereodecoder is se- lected the decoder remains muted and the mpx pin is connected to vref to avoid any discharge of the coupling capacitor through leakage currents. ingain + infilter the ingain stage allows to adjust the mpx signal to a magnitude of about 1vrms internally which is the recommended value. the 4th order input filter has a corner frequency of 80khz and is used to attenuate spikes and nose and acts as an anti al- lasing filter for the following switch capacitor fil- ters. demodulator in the demodulator block the left and the right channel are separated from the mpx signal. in this stage also the 19 khz pilot tone is cancelled. for reaching a high channel separation the TDA7400d offers an i2c bus programmable roll- off adjustment which is able to compensate the lowpass behaviour of the tuner section. if the tuner attenuation at 38khz is in a range from 13.8% to 24.6% the TDA7400d needs no exter- nal network in front of the mpx pin. within this range an adjustment to obtain at least 40db channel separation is possible. the bits for this adjustment are located together with the fieldstrength adjustment in one byte. this gives the possibility to perform an optimization step during the production of the carradio where the channel separation and the fieldstrength con- trol are trimmed. the setup of the stereoblend characteristics which is programmable in a wide range is de- scribed in 2.8. ingain 3.5 ... 11db step 2.5db infilter lp 80khz 4.th order demodulator - plot canc - roll-off comp. - lp 25khz pll + pilot-det. f19 noise blanker f38 stereo holdn sb control deemphasis + highcut t=50 or 75 m s ref 5v vsbl mpinfl level intern hc control vhcch vhccl - multipath detector d a mp_out level input lp 2.2khz 1.th order mp_in level fm_l fm_r mpx 100k d98au855 gain 0..10db mplevelout quality detector qual noise + figure 12. block diagram of the stereodecoder TDA7400 15/28
deemphasis and highcut. the lowpass filter for the deemphasis allows to choose between a time constant of 50 m s and 75 m s (bit d 7 , stereodecoder byte). the highcut control range will be in both cases t hc =2 ? t deemp . inside the highcut control range (between vhch and vhcl) the level signal is converted into a 5 bit word which controls the lowpass time constant between t deemp ...3 ? t deemp . there by the resolution will remain always 5 bits independently of the absolute voltage range between the vhch and vhcl values. the highcut function can be switched off by i 2 c bus (bit d 7 , fieldstrength byte set to o0o). the setup of the highcut characteristics is de- scribed in 2.9. pll and pilot tone detector the pll has the task to lock on the 19khz pilo- tone during a stereo transmission to allow a cor- rect demodulation. the included detector enables the demodulation if the pilot tone reaches the se- lected pilot tone threshold v pthst . two different thresholds are available. the detector output (sig- nal stereo, see block diagram) can be checked by reading the status byte of the TDA7400d via i 2 c bus. fieldstrength control the fieldstrength input is used to control the high cut and the stereoblend function. in addition the signal can be also used to control the noise- blanker thresholds and as input for the multipath detector. these additional functions are de- scribed in sections 3.3 and 4. level input and gain to suppress undesired high frequency modula- tion on the highcut and stereoblend function the level signal is lowpass filtered firstly. the filter is a combination of a 1st order rc low- pass at 53khz (working as anti-aliasing filter) and a 1st-order switched capacitor lowpass at 2.2khz. the second stage is a programmable gain stage to adapt the level signal internally to different if device (see testmode section 5 levelintern). the gain is widely programmable in 16 steps from 0db to 10db (step = 0.67db). these 4 bits are located together with the roll-off bits in the ostereodecoder adjustmento byte to simplify a possible adaptation during the production of the carradio. stereoblend control the stereoblend control block converts the inter- nal level voltage (level intern) into an de- modulator compatible analog signal which is used to control the channel separation between 0db and the maximum separation. internally this con- trol range has a fixed upper limit which is the in- ternal reference voltage ref5v. the lower limit can be programmed between 29.2% and 58%, of ref5v in 4.167% steps (see figs. 11, 12). to adjust the external level voltage to the inter- nal range two values must be defined: the level gain l g and vsbl (see fig. 12). to adjust the voltage where the full channel separation is reached (vst) the level gain l g has to be de- fined. the following equation can be used to esti- mate the gain: softmute command std mute v o t d97au638 t t figure 13. signals during stereodecoder's softmute figure 14. internal stereoblend characteristics TDA7400 16/28
l g = ref5v fieldstrength voltage[stereo] the gain can be programmed through 4 bits in the ostereodecoder-adjustmentobyte. the mono voltage vmo (0db channel separa- tion) can be choosen selecting vsbl all necessary internal reference voltages like ref5v are derived from a bandgap circuit. therefore they have a temperature coefficient near zero. this is useful if the fieldstrength signal is also temperature compensated. but most if devices apply a level voltage with a tc of 3300ppm. the TDA7400d offers this tc for the reference voltages, too. the tc is select- able with bit d 7 of the ostereodecoder adjustmento byte. highcut control the highcut control setup is similar to the stereoblend control setup : the starting point vhch can be set with 2 bits to be 42, 50, 58 or 66% of ref5v whereas the range can be set to be 17, 22, 28 or 33% of vhch (see fig. 21). functional description of the noise- blanker in the automotive environment the mpx signal is disturbed by spikes produced by the ignition and for example the wiper motor. the aim of the noiseblanker part is to cancel the audible influ- ence of the spikes. therefore the output of the stereodecoder is held at the actual voltage for a time between 22 and 38 m s (programmable). the block diagram of the noiseblanker is given in fig.17. in a first stage the spikes must be detected but to avoid a wrong triggering on high frequency (white) noise a complex trigger control is imple- mented. behind the triggerstage a pulse former generates the oblankingo pulse. to avoid any crosstalk to the signalpath the noiseblanker is supplied by his own biasing circuit. trigger path the incoming mpx signal is highpass filtered, amplified and rectified. this second order high- pass-filter has a corner frequency of 140khz. the rectified signal, rect, is lowpass filtered to generate a signal called peak. also noise with a frequency 140khz increases the peak voltage. the resulting voltage can be adjusted by use of the noise rectifier discharge current. the peak voltage is fed to a threshold generator, which adds to the peak voltage a dc depend- ent threshold vth. both signals, rect and internal voltages t d97au639 vsbl ref 5v setup of vst internal voltages t 33% ref 5v setup of vmo level level intern fieldstrenght voltage vst vmo level intern 42% 50% 58% vsbl vst vmo fieldstrenght voltage figure 15. relation between internal and external level voltage and setup of stereoblend lowpass time constant d97au640 t deemp fieldstrenght vhch vhcl 3 ? t deemp figure 16. highcut characteristics TDA7400 17/28
peak+vth are fed to a comparator which trig- gers a re-triggerable monoflop. the monoflop's output activates the sample-and-hold circuits in the signalpath for selected duration. automatic noise controlled threshold adjust- ment (atc) there are mainly two independent possibilities for programming the trigger threshold: a the low threshold in 8 steps (bits d 0 to d 2 of the noiseblanker byte) b the noise adjusted threshold in 4 steps (bits d 3 and d 4 of the noiseblanker byte, see fig. 14). the low threshold is active in combination with a good mpx signal without any noise; the peak voltage is less than 1v. the sensitivity in this op- eration is high. if the mpx signal is noisy the peak voltage in- creases due to the higher noise, which is also rectified. with increasing of the peak voltage the trigger threshold increases, too. this particular gain is programmable in 4 steps (see fig. ...). automatic threshold control mecha- nism automatic threshold control by the stereoblend voltage besides the noise controlled threshold adjust- ment there is an additional possibility for influenc- ing the trigger threshold. it is depending on the stereoblend control. the point where the mpx signal starts to become noisy is fixed by the rf part. therefore also the starting point of the normal noise-controlled trig- ger adjustment is fixed (fig. 11). in some cases the behaviour of the noiseblanker can be im- proved by increasing the threshold even in a re- gion of higher fieldstrength. sometimes a wrong triggering occures for the mpx signal often shows distortion in this range which can be avoided even if using a low threshold. because of the overlap of this range and the range of the stereo/mono transition it can be con- trolled by stereoblend. this threshold increase is programmable in 3 steps or switched off with bits d 0 and d 1 of the fieldstrength control byte. over deviation detector if the system is tuned to stations with a high de- viation the noiseblanker can trigger on the higher frequencies of the modulation. to avoid this wrong behaviour, which causes noise in the out- put signal, the noiseblanker offers a deviation de- pendent threshold adjustment. by rectifying the mpx signal a further signal rep- resenting the actual deviation is obtained. it is used to increase the peak voltage. offset and gain of this circuit are programmable in 3 steps with the bits d 6 and d 7 of the stereodecoder byte (the first step turns off the detector, see fig. 15). functional description of the multi- path detector using the internal multipath detector the audible effects of a multipath condition can be minimized. a multipath condition is detected by rectifying the 19khz spectrum in the fieldstrength signal. an external capacitor is used to define the attack and decay times (see block diagram fig. 23). the + - rectifier lowpass rect + + threshold generator vth peak additional threshold control monoflop holdn mpx d98au856 mpx control figure 17. block diagram of the noiseblanker TDA7400 18/28
mpout pin is used as detector output connected to a capacitor of about 47nf and additionally the mpin pin is selected to be the fieldstrength input. using the configuration an external adaptation to the user's requiremet is given in fig.25. selecting the ointernal influenceo in the configura- tion byte, the channel separation is automatically reduced during a multipath condition according to the voltage appearing at the mp_out pin. a possible application is shown in fig. 26. programming to obtain a good multipath performance an adap- tation is necessary. therefore tha gain of the 19khz bandpass is programmable in four steps as well as the rectifier gain. the attack and decay times can be set by the external capacitor value. quality detector the TDA7400d offers a quality detector output which gives a voltage representing the fm recep- tion conditions. to calculate this voltage the mpx noise and the multipath detector output are summed according to the following formula: quality = 1.6 (v noise -0.8v)+ a (ref5v- v mpout ) the noise signal is the peak signal without addi- tional influences. the factor oao can be pro- grammed from 0.7 to 1.15. the output is a low im- pedance output able to drive external circuitry as well as simply fed to an a/d converter for rds applications. test mode during the test mode which can be activated by setting bit d 0 of the testing byte and bit d 5 of the subaddress byte to o1o several internal signals are available at the cassr pin. during this mode the input resistor of 100kohm is disconnected from the pin. the internal signals available are shown in the software specification. i 2 c bus interface description interface protocol the interface protocol comprises: -a start condition (s) -a chip address byte (the lsb bit determines read / write transmission) -a subaddress byte -a sequence of data (n-bytes + acknowledge) -a stop condition (p) rectifier bandpass 19khz - to sb d98au857 mp_in gain 2 bits gain 2 bits charge 1 bit vdd mpout level int. influence 47nf figure 18. block diagram of the multipath detector TDA7400 19/28
d97au627 s1000110r/wack ack ackp msb lsb msb lsb msb lsb chip address xi subaddress data 1 to data n az t a3 a2 a1 a0 data s = start ack = acknowledge az = autozero-remain t = testing i = autoincrement p = stop max clock speed 500kbits/s the transmitted data is automatically updated af- ter each ack. transmission can be repeated without new chip address. auto increment if bit i in the subaddress byte is set to o1o, the autoincrement of the subaddress is enabled. transmitted data (send mode) msb lsb xxxxstsmxx sm = 1 soft mute activated st = 1 stereo mode x = not used subaddress (receive mode) msb lsb function i3 i2 i1 i0 a3 a2 a1 a0 0 1 antiradiation filter off on 0 1 autozero remain off on 0 1 testmode off on 0 1 auto increment mode off on 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 databyte addressing input selector volume treble bass speaker attenuator lf speaker attenuator rf speaker attenuator lr speaker attenuator rr softmute / bass prog. stereodecoder noiseblanker high cut control fieldstrength & quality configuration stereodecoder adjustment testing TDA7400 20/28
data byte specification input selector (subaddress 0h) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 source selector cd cassette phone am stereo decoder ac inputs front mute ac inputs rear 0 0 : 1 1 0 0 : 1 1 0 0 : 1 1 0 1 : 0 1 in-gain 15db 14db : 1db 0db 0 1 coupl. front speaker external internal volume and speaker attenuation (subaddress 1h, 4h, 5h, 6h, 7h) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 1 : 1 1 0 : 0 0 0 : 0 0 1 : 1 1 1 : 0 0 1 : 0 0 1 : 0 0 1 : 1 0 not used configurations 1 : 1 0 0 0 : 0 0 : 0 0 0 : 0 0 0 0 : 0 0 : 1 1 0 : 0 0 0 0 : 0 0 : 0 0 0 : 0 0 0 0 : 0 1 : 0 0 1 : 0 0 0 0 : 1 0 : 1 1 1 : 0 0 0 0 : 1 0 : 1 1 1 : 0 0 0 0 : 1 0 : 1 1 1 : 1 0 0 1 : 1 0 : 0 1 +15db : +1db 0db 0db -1db : -15db -16db : -78db -79db x 1 1 x x x x x mute TDA7400 21/28
treble filter (subaddress 2h) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 : 0 0 1 1 : 1 1 0 0 : 1 1 1 1 : 0 0 0 0 : 1 1 1 1 : 0 0 0 1 : 0 1 1 0 : 1 0 treble steps -15db -14db : -1db 0db 0db +1db : +14db +15db 0 0 1 1 0 1 0 1 treble center frequency 10.0khz 12.5khz 15.0khz 17.5khz 0 1 coupl. rear speaker external (ac) internal bass filter (subaddress 3h) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 : 0 0 1 1 : 1 1 0 0 : 1 1 1 1 : 0 0 0 0 : 1 1 1 1 : 0 0 0 1 : 0 1 1 0 : 1 0 bass steps -15db -14db : -1db 0db 0db +1db : +14db +15db 0 0 1 1 0 1 0 1 bass q-factor 1.0 1.25 1.50 2.0 0 1 bass dc mode off on TDA7400 22/28
stereodecoder (subaddress 9h) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 std unmuted std muted 0 1 1 0 in gain 8.5db in gain 6db others combinations not used 1 must be o1o 0 1 forced mono mono/stereo switch automatically 0 1 noiseblanker peak charge current low noiseblanker peak charge current high 0 1 pilot threshold high pilot threshold low 0 1 deemphasis 50 m s deemphasis 75 m s soft mute and bass programming (subaddress 8h) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 0 0 1 1 0 1 0 1 0 1 mute enable soft mute disable soft mute mutetime = 0.48ms mutetime = 0.96ms mutetime = 40.4ms mutetime = 324ms stereodecoder soft mute influence = on stereodecoder soft mute influence = off 0 0 1 1 1 0 1 0 1 1 bass center frequency center frequency = 60 hz center frequency = 70 hz center frequency = 80 hz center frequency = 100hz center frequency = 150hz (1) 0 0 1 1 0 1 0 1 noise blanker time center frequency = 38 m s center frequency = 25.5 m s center frequency = 32 m s center frequency = 22 m s (1) only for bass q-factor = 2.0 TDA7400 23/28
noiseblanker (subaddress ah) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 low threshold 65mv low threshold 60mv low threshold 55mv low threshold 50mv low threshold 45mv low threshold 40mv low threshold 35mv low threshold 30mv 0 0 1 1 0 1 0 1 noise controlled threshold 320mv noise controlled threshold 260mv noise controlled threshold 200mv noise controlled threshold 140mv 0 1 noise blanker off noise blanker on 0 0 1 1 0 1 0 1 over deviation adjust 2.8v over deviation adjust 2.0v over deviation adjust 1.2v over deviation detector off high cut (subaddress bh) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 high cut off high cut on 0 0 1 1 0 1 0 1 max. high cut 2db max. high cut 5db max. high cut 7db max. high cut 10db 0 0 1 1 0 1 0 1 vhch at 42% ref 5v vhch at 50% ref 5v vhch at 58% ref 5v vhch at 66% ref 5v 0 0 1 1 0 1 0 1 vhcl at 16.7% vhch vhcl at 22.2% vhch vhcl at 27.8% vhch vhcl at 33.3% vhch 0 1 strong multipath influence on peak 18k off on (18k discharge if v mpout <2.5v) TDA7400 24/28
configuration (subaddress dh) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 1 1 0 1 0 1 noise rectifier discharge resistor r = infinite r = 56k w r = 33k w r =18k w 0 1 0 1 0 0 1 1 multipath detector bandpass gain 6db 12db 16db 18db 0 1 multipath detector internal influence on off 0 1 multipath detector charge current 0.5 m a multipath detector charge current 1 m a 0 0 1 1 0 1 0 1 multipath detector reflection gain gain = 7.6db gain = 4.6db gain = 0db disabled fieldstrength control (subaddress ch) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 vsbl at 29% ref 5v vsbl at 33% ref 5v vsbl at 38% ref 5v vsbl at 42% ref 5v vsbl at 46% ref 5v vsbl at 50% ref 5v vsbl at 54% ref 5v vsbl at 58% ref 5v 0 0 1 1 0 1 0 1 noiseblanker field strength adj 2.3v noiseblanker field strength adj 1.8v noiseblanker field strength adj 1.3v noiseblanker field strength adj off 0 0 1 1 0 1 0 1 quality detector coefficient a = 0.7 quality detector coefficient a = 0.85 quality detector coefficient a = 1.0 quality detector coefficient a = 1.15 0 1 multipath off influence on peak discharge -1v/ms (at mpout = 2.5v TDA7400 25/28
stereodecoder adjustment (subaddress eh) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 : 1 : 1 0 0 1 : 0 : 1 0 1 0 : 0 : 1 roll off compensation not allowed 19.6% 21.5% : 25.3% : 31.0% 0 0 0 : 1 0 0 0 : 1 0 0 1 : 1 0 1 0 : 1 level gain 0db 0.66db 1.33db : 10db 1 must be o1o testing (subaddress fh) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 stereodecoder test signals off test signals enabled if bit d5 of the subaddress (test mode bit) is set to o1o, too 0 1 external clock internal clock 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 testsignals at cass_r vhcch level intern pilot magnitude vcocon; vco control voltage pilot threshold holdn nb threshold f228 vhccl vsbl not used not used peak not used ref5v not used 0 1 vco off on 0 1 audioprocessor test mode enabled if bit d5 of the subaddress (test mode bit) is set to o1o off note : this byte is used fortesting or evaluation purposes only and must not be set to other values than the default o11111110o in the application! TDA7400 26/28
tqfp44 (10 x 10) dim. mm inch min. typ. max. min. typ. max. a 1.60 0.063 a1 0.05 0.15 0.002 0.006 a2 1.35 1.40 1.45 0.053 0.055 0.057 b 0.30 0.37 0.45 0.012 0.014 0.018 c 0.09 0.20 0.004 0.008 d 12.00 0.472 d1 10.00 0.394 d3 8.00 0.315 e 0.80 0.031 e 12.00 0.472 e1 10.00 0.394 e3 8.00 0.315 l 0.45 0.60 0.75 0.018 0.024 0.030 l1 1.00 0.039 k 0 (min.), 3.5 (typ.), 7 (max.) a a2 a1 b seating plane c 11 12 22 23 33 34 44 e1 e d1 d e 1 k b tqfp4410 l 0.10mm .004 outline and mechanical data TDA7400 27/28
information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specification mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicroelectronics. the st logo is a registered trademark of stmicroelectronics ? 1999 stmicroelectronics printed in italy all rights reserved stmicroelectronics group of companies australia - brazil - china - finland - france - germany - hong kong - india - italy - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - u.s.a. http://www.st.com TDA7400 28/28

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